We have now to treat of the
Pachyglossa,
Which are those Lizards which have the tongue short, thick, attached to the gullet, and not exsertile. These fall under two very distinct tribes—the Strobilosaura and Nyctisaura of Dr. Gray, or the tribe of the Iguanas and their kindred, and that of the Geckos and their kindred. The tribe of
Strobilosaura
Have the scales of the back and sides imbricate, generally rhombic, and those of the lower parts imbricate and of small size. Tail with more or less distinct whorls of scales. The eyes diurnal, with round pupil, and valvular lids. Feet with toes of very unequal length. Many of these reptiles have a row of spines or spine-like scales along the back and tail, which in some are very long, while others have high dorsal and caudal crests, an expansile gular pouch, or other adornments. Like the Varans among the Leptoglossa (p. 114), these Lizards do not renew the tail, or a portion of it, after mutilation. There are two great families of them—one peculiar to the Old World with Australia, the other to the New World; but as families they do not differ much, and might very well be retained as divisions of the same extensive family.
In the family of Iguanidæ, all of which inhabit America or its islands, the teeth are round at the root, dilated and compressed at the tip, and toothed at the edge; they are placed in a simple series on the inner side of the jaws, just below the edge, and are covered on the inner side by the gums; as they fall out they are replaced by others, which grow at the base of their predecessors, and gradually cause the absorption of their roots. Probably not fewer than a hundred and fifty species are now recognised, which are distributed under more than fifty genera. We can only notice a few of the most remarkable of these Lizards, some of the larger of which attain a length of five or six feet, with proportionate bulk of body. As a general rule, the larger species are mainly herbivorous, while the smaller are chiefly insectivorous, though many of the latter also devour fruit. As most of them are remarkable for their rapid changes of colouring, the name of Chameleon is often misapplied to them, in the supposition that the Chameleons are the only Lizards in which that curious phenomenon is observable. In one remarkable species, the Sphærops anomalus, inhabiting Brazil, it is stated that the eye nearly resembles that of the true Chameleons, and it is also one of those which are particularly celebrated for its changes of hue.]
Fig. 28.—Iguana tuberculata.
The name Iguana was given by Laurenti to a heterogeneous group of Saurians, various forms being included which were first separated by Daudin. The Iguanas, as thus restricted, are characterized by a very large thin dew-lap under the neck, a double row of small palatal teeth, and a crest on the back and tail; the latter long, slender, compressed, and covered with small imbricated and carinated scales. Messrs. Duméril and Bibron describe the genus, thus modified, as principally remarkable for the cutaneous prolongation which constitutes the deep and thin dew-lap, or pouch, the free border of which describes a curved line, and is dentated at the part nearest the chin. The head is moderately long, and has the form of a pyramid with four faces. The neck is slightly compressed, the limbs long, the toes unequal and sometimes denticulate on the edge. The five toes of the posterior feet are graduated; the tail, which is long and slender, is slightly flattened from right to left. The Iguanas live chiefly on trees, but they take readily to the water, swimming with great facility.
There are numerous species, all of which are found in South America and the Antilles. In the Island of Isabella, Sir E. Belcher found swarms of them which he had reason to consider omnivorous, feeding voraciously on birds' eggs and the intestines of birds and insects.